This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. ABSTRACT The overall goal of this study is to examine whether patients with skeletal dysplasias have alterations in bone mineral density when compared to the general population of similar age. Skeletal dysplasias are a heterogeneous group of disorders characterized by abnormalities in the growth and development of the skeleton. The include the osteodysplasias, associated with primary alterations of bone strength and integrity, and chondrodysplasias which affect the cartilage, and hence, the shape and longitudinal growth of the skeleton. This is proposed as a pilot study since there are no preliminary data describing bone densities in this population of patients. Measurement of the bone mass density in these subjects will be performed in a reliable way using dual-energy X-ray absorptiometry (DXA scanning). Analysis of the results will allow us to design further research protocols to establish correlations between gene mutations and alterations in mineral deposition. Moreover, this data will provide a baseline for prospective studies aimed at determining the effects of different interventions for the managemnt of these patients. HYPOTHESIS Our general hypothesis is that patients with skeletal dysplasias may have alterations in bone mineral density when compared to the general population of similar age and gender. SPECIFIC AIMS The purpose of this study is to determine whether patients with skeletal dysplasias have differences in bone mineral density from the general population of similar age and gender. This knowledge will enable us to further delineate the natural histories of these conditions, and to identify those patients at risk for decreased bone mineral density so that effective, timely treatment may be offered. This is proposed as a pilot, cross sectional study since there are no preliminary data describing bone densities in this population of patients. Analysis of the results will also allow us to design further research protocols looking at the issue of bone density in the different diseases that comprise skeletal dysplasias, and to establish correlations between gene mutations and alterations in mineral deposition. Moreover, this data will provide a baseline for prospective studies aimed at determining the effects of different interventions for the management of these patients.